Heat exchanger for liquid at overpressure

ABSTRACT

A heat exchanger for liquid under pressure in which a casing is divided by a partition into large and small chambers, with a heat surface being located within the small chamber and the chambers being in communication via an opening. The upper portion of the partition is provided with a valve means for conducting gas from the small chamber to the large chamber, with the valve means being so constructed that the difference in pressure between the gas-filled upper portion of the small chamber and the corresponding level in the large chamber, and which pressure arises upon the opening of an outflow valve for the outlet of the large chamber, is sufficient for pressing at least a part of the gas included in the small chamber out through the valve member.

United States Patent 1191 Hecktor HEAT EXCHANGER FOR LIQUID AT OVERPRESSURE [75] Inventor: Bengt-Olof Ingemar Hecktor,

Bjarred, Sweden [73] Assignee: AB Gustavsbergs Fabriker,

Gustavsberg, Sweden [22] Filed: Sept. 8, 1972 [21] Appl. No.: 287,571 g Jan. 1,1974

Primary Examiner-Albert W. Davis, Jr. Attorney-John C. Holman et al.

[57] ABSTRACT A heat exchanger for liquid under pressure in which a casing is divided by a partition into large and small chambers, with a heat surface being located within the small chamber and the chambers being in communication via an opening. The upper portion of the partition is provided with a valve means for conducting gas from the small chamberto the large chamber, with the valve means being so constructed that the difference in pressure between the gas-filled upper portion of the small chamber and the corresponding level in the large chamber, and which pressure arises upon the openingof an outflow valve for the outlet of the large chamber, is sufficient for pressing at least a part of the gas included in the small chamber out through the valve member.

11 Claims, 5 Drawing Figures HEAT EXCHANGER FOR LIQUID AT OVERPRESSURE BACKGROUND or THE INVENTION This invention relates to'a heat exchanger preferably of the storage type, which is used particularly for preparing hot consumption water under a certain overpressure.

At the heating of certain types of comsumption water, deposits develop on the heat transferring surface which can giverise to corrosion damage in the material of said surface. The heat transferring surface usually is an electric immersion heater, but it may also be, for example, a distance heating coil. Owing to the deposits on the electric immersion heater, the heater is destroyed within a short time by burning due to overheating, while deposits on a distance heating coil bring about a decrease in the heat transfer effect. One way of reducing the aforesaid disadvantages is by means of a partition wall to divide the volume of the heat exchanger into a large chamber and a small chamber which are separated from each other by a thin partition wall having a large surface, and in which the surface which supplies heat to the apparatus, i.e. the primary heat surface, is placed in the small chamber. The small chamber and the large chamber communicate with each other via an opening preferably arranged below the uppermost portion of the primary heat surface. The liquid in the small chamber and in the large chamber thereby have the same pressure. The heat from the primary ter. In a heat exchanger ofv storage type for this purpose, the pressure is normally up to about 9 gauge pressure. At this pressure the solubility of air aha other gases in water is of the magnitude 0.2 liter gas of atmospheric pressure per liter water. When tapping a large quantity of hot water, the pressure in the heat exchanger may drop to about 0.5 gauge pressure, at which the solubility of gas only is about 0.05 liter air per liter water, so that a great gas quantity goes off in the form of gas bubbles and is collected as a gas cushion in the uppermost portion of the small chamber,

When the small chamber has a volume of, for example, 5 liters, the size of the gas cushion is about 1.5 liter at 0.5 gauge pressure, and this water volume thus is pressed out of the small chamber into the large chamber. When the tapping of hot water is stopped, the pressure again rises to 9 gauge pressure whereby the gas cushion in the first hand is compressed to a volume of about 0.25 liter, and 1.25 liter fresh water passes from the large chamber into the small chamber. When at this time no venting is effected, the gas will gradually be heat surface is transferred first to the liquid in the small chamber and thereafter via the partitionwall out into the liquid in the large chamber. Both the inlet and outlet for the liquid to be heated are situated in the large chamber. The risk of corrosion and deposit formation on the primary heat surface is reduced still more by placing the opening between the large and small chamber on a low level.

In known heat exchangers air and other gases are led off from the small chamber in such a way, that the small chamber is provided with a manually or automatically controlled connection extending from the upper portion of the chamber to-the ambient atmosphere. The automatic venting, in order not to be too expensive, requires a connection between the air pocket and ambient atmosphere in such a way, that the air ascends to the venting device. This implies the necessity of arranging a fixed connection from the partition wall between the small chamber and the large chamber and the easing of the heat exchanger. This in its turn renders it difficult, for example, to use flexible material for the partition wall and to connect this partition wall rigidly with an exchangeable primary heat surface. A manual venting device can be constructed such that the partition wall is rigidly connected with an exchangeable primary heat surface, but a heat exchanger where in which the liquid is under overpressure, i.e. where the flow is controlled by a valve means in the outlet conduit from the heat exchanger, will not operate satisfactorily. In that case, great pressure variations can occur in the heat exchanger and thereby the liquid exchange in the small chamber will be increased considerably, due to the gas which possibly is included in the small chamber and is released from the liquid at pressure reduction and expands at the pressure reduction. As an example thereof may be mentioned electric heating of consumption wasoluted again and at the next tapping the procedure is repeated.

Owing to the procedure described above, the water exchange in the small chamber may be l0 to 20 per cent instead of about 2 per cent as calculated, because of the normal thermal expansion of the water, i.e. the exchange may be 5 to 10 timesgreater than calculated.

The aforesaid degassing problems, however, are solved effectively and at low costs by the present invention used at the basic construction of a heat exchanger referred to above.

SUMMARY OF THE INVENTION The invention comprises a valve means which at a large accumulation of gas in the small chamber, i.e. at overpressure in the upper portion of the small chamber compared with the corresponding level in the large chamber, allows all of the gas or a part thereof to pass from the small chamber into the large chamber. The valve means may be a single valve member placed in the upper portion of the partition wall between the small chamber and the large chamber. The valve means according to another embodiment may comprise two valve members, one upper valve member and one lower one, of which the upper valve member is combined with a valve member arranged further down in the small chamber such that all of the water or a certain part thereof, and possibly gas, is located between said two valve members, and the lower valve member has a very low resistance in the flow direction to the upper valve member in relation to said upper valve member while the flow resistance in the opposite direction is so high that it gives rise to an increased overpressure in the space between the valve members when gas is released or expands in said space, and thereby the outflow of gas through the upper valve member is facilitated still more. In this way, the pressure variations which give rise to problems at heat exchangers without the present invention are utilized by the invention for eliminating the problem.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is described in greater detail with reference to the accompanying drawing showing several embodiments of the invention.

FIG. II is a view partly in elevation and partly in crosssection of one embodiment of the invention,

FIG. 2 is a view similar to FIG. 1 of another embodiment,

FIG. 3 is a fragmentary view in cross-section of a further embodiment of a valve member,

FIG. 4 is a view similar to FIG. 3 of yet another embodiment and,

FIG. 5 is a view along the lines of FIGS. 1 and 2 of another embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS InFIG. 1 within a casing 1 a valve member 7 for conducting gas from a small chamber to a large chamber 9 is placed in the upper portion of a partition wall 5. The valve member 7 a capillary tube such that owing to counteracting capillary and surface tension forces not all of the gas in the small chamber 10 passes by its own force into the large chamber. The capillary tube Y may be inserted in a holder of, of example, plastic or rubber material in order to facilitate its mounting in the wall 5 which simply can be carried out by cutting a large hole in the flexible wall 5 which thereafter is laced up about the capillary tube.

The valve member can be completed by a valve member 8 of a lower location above a primary heat sur face 2, thereby separating off a small liquid volume between the two valve members 7, 8. The valve 8 of lower location may comprise a seat with a relatively large opening area and an easily movable part allowing the passage of liquid.

FIG. 2 shows anotherembodiment at which the valve member 7 is a hole of such a small size in the wall 5 that owing to counteracting capillary and surface tension forces not all of the gas passes out into the large chamber. The valve means may also be completed by the valve member 8 of a lower location which in this em bodiment is placed in the immediate vicinity of a connection opening 6 between the two chambers 10, 9 and is defined by a seat and a ball-shaped sealing body. In FIG. 2 the sealing body must have the same or a higher specific weight than the liquid, but one may also imagine a mounting with a suspended sealing body having a lower specific weight than the liquid, in which case the valve seat is turned through l80relative to what is shown in FIG. 2.

FIG. 3 shows an embodiment at which the valve member 7 is built up of a tubular member 11 with a relatively large vent hole and a tightly fitting elastic outer casing 12 which at overpressure in the small chamber 10 expands and allows gas to pass out. The valve means may also be completed bya lower valve member 8 comprising a seat 13, the lower surfaces of which are inclined to the vent hole in order to ensure effective venting, and a closing member 14 which is a spindle valve or the ike.

The valve means in FIG. 4 comprises the valve member 7, which is located in the partition wall 5 and built up of a valve seat 16, the lower surfaces of which are inclined to the vent hole in order to ensure effective venting. The valve seat 16 in this case is a part of the partition wall 5 between the small and the large chamber 10, 9.

FIG. 5 shows an embodiment at which the valve means is built up of the two valve members 7, 8 assembled into a unit 17 constituting a part of the partition wall 5. A cavity 18 for collecting gas is located between the two valve members 7, 8.

I claim:

1. A heat exchanger for liquid under pressure, preferably of the storage type, a casing, said casing being divided into a large chamber and a small chamber by a.

partition wall, a heating means having a surface arranged within the small chamber which supplies heat from outside to the heat exchanger, said partition wall having a large surface compared with said heating means surface arranged within the small chamber, said two chambers communicating with each other via an opening, and the large chamber being provided with an inlet and an outlet for the liquid to be heated having an outflow valve, characterized in that the upper portion of the partition wall between the small chamber and the large chamber is provided with a first valve means for conducting gas from the small chamber to the large chamber, and said first valve means being so constructed that the difference in pressure between the gas-filled upper portion of the small chamber and the corresponding level in the large chamber, which pressure difference arises upon the opening of said outflow valve, is sufficient for pressing at least a part of the gas amount included in the small chamber out through the first valve means.

2. The heat exchanger according to claim 1, characterized in that the small chamber is provided with a second valve means located below the first valve means, which second valve means has a low flow resistance in the direction to the first valve means and a substantial flow resistance in the opposite direction and thereby increases the pressure difference between that portion of the small chamber which includes the gas and the corresponding level in the large chamber when upon the opening of the outflow valve the pressure in the large chamber drops.

3. The heat exchanger according to claim 1, characterized in that the first valve means located in the partition wall for conducting gas from the small chamber to the large chamber is a capillary tube so designed that the gas in the small chamber due to counteracting capillary forces and surface tension forces is prevented from passing out to' the large chamber by the force of its own.

4. The heat exchanger according to claim 1, characterized in that the first valve means is a hole of such a dimension that all of the gas in the small chamber due to counteracting capillary forces and surface tension forces is prevented to pass to the large chamber by the force of its own. I

5. The heat exchanger according to claim 1, charac- I terized in that the first valve means is a taphole, a cut or a slit in a portion of the partition wall which is made of an elastic material, and the hole or cut in the absence of over-pressure in the uppermost portion of the small chamber is closed by the properties of the wall material.

6. The heat exchanger according to claim 1, characterized in that the first valve means is a valve allowing flow in the direction from the small chamber to the large chamber.

7. The heat exchanger according to claim 2, characterized in that the further valve member is arranged in connection to the connecting opening between the large chamber and the small chamber.

lection and expansion of gas.

10. The heat exchanger according to claim 2, characterized in that the second valve means is a stop valve allowing the flow of gas and liquid only in the direction to the first valve means.

11. The heat exchanger according to claim 1, characterized in that the partition wall between the small chamber and the larger chamber is made of a flexible material. 

1. A heat exchanger for liquid under pressure, preferably of the storage type, a casing, said casing being divided into a large chamber and a small chamber by a partition wall, a heating means having a surface arranged within the small chamber which supplies heat from outside to the heat exchanger, said partition wall having a large surface compared with said heating means surface arranged within the small chamber, said two chambers communicating with each other via an opening, and the large chamber being provided with an inlet and an outlet for the liqUid to be heated having an outflow valve, characterized in that the upper portion of the partition wall between the small chamber and the large chamber is provided with a first valve means for conducting gas from the small chamber to the large chamber, and said first valve means being so constructed that the difference in pressure between the gas-filled upper portion of the small chamber and the corresponding level in the large chamber, which pressure difference arises upon the opening of said outflow valve, is sufficient for pressing at least a part of the gas amount included in the small chamber out through the first valve means.
 2. The heat exchanger according to claim 1, characterized in that the small chamber is provided with a second valve means located below the first valve means, which second valve means has a low flow resistance in the direction to the first valve means and a substantial flow resistance in the opposite direction and thereby increases the pressure difference between that portion of the small chamber which includes the gas and the corresponding level in the large chamber when upon the opening of the outflow valve the pressure in the large chamber drops.
 3. The heat exchanger according to claim 1, characterized in that the first valve means located in the partition wall for conducting gas from the small chamber to the large chamber is a capillary tube so designed that the gas in the small chamber due to counteracting capillary forces and surface tension forces is prevented from passing out to the large chamber by the force of its own.
 4. The heat exchanger according to claim 1, characterized in that the first valve means is a hole of such a dimension that all of the gas in the small chamber due to counteracting capillary forces and surface tension forces is prevented to pass to the large chamber by the force of its own.
 5. The heat exchanger according to claim 1, characterized in that the first valve means is a taphole, a cut or a slit in a portion of the partition wall which is made of an elastic material, and the hole or cut in the absence of over-pressure in the uppermost portion of the small chamber is closed by the properties of the wall material.
 6. The heat exchanger according to claim 1, characterized in that the first valve means is a valve allowing flow in the direction from the small chamber to the large chamber.
 7. The heat exchanger according to claim 2, characterized in that the further valve member is arranged in connection to the connecting opening between the large chamber and the small chamber.
 8. The heat exchanger according to claim 2, characterized in that the second valve means is so arranged and constructed that it divides the small chamber into two volumes, the lower volume including the surface and the upper volume including the first valve means.
 9. The heat exchanger according to claim 2 characterized in that the second valve means is assembled with the first valve means into a unit which forms a portion of the partition wall between the small chamber and the large chamber and includes a cavity for the collection and expansion of gas.
 10. The heat exchanger according to claim 2, characterized in that the second valve means is a stop valve allowing the flow of gas and liquid only in the direction to the first valve means.
 11. The heat exchanger according to claim 1, characterized in that the partition wall between the small chamber and the larger chamber is made of a flexible material. 